What point are you in the game? And if you're beyond the first transfer window, it depends who you've signed and got rid of.
The problem is, if you've got pretty much the same squad as at the start, you already have Kagawa, Young and Nani. All of these players can play on the left, and if you play Valencia a lot on the right, it's a choice between the 3 of them. I don't think you need more options out wide.
What I would do is keep Welbeck as a backup striker, (on what I think is a fairly low wage for him) and maybe train his composure. He's still young, so if you can build on the pace and ability to close down he has, with more clinical finishes in front of goal, I think you're onto another top striker.
You've got more than enough options out wide IMO, but having 4 class strikers will be key in the latter phases of the season if you're in multiple competitions.